Mixer with mixer drum equipped with mixing blades located on a central drive shaft



June 23, 1970 P. STIFT 3,516,646

MIXER WITH MIXER DRUM EQUIPPED WITH MIXING BLADES LOCATED ON A CENTRALDRIVE SHAFT Filed Oct. 30, 196' 2 Sheets-Sheet l r w. 1 x V 4% 2 F/ 17 IK. All l l5 lnvenfor PAU\ 81TH" June 23, 1970 sTlFT 3,516,646

MIXER WITH MIXER DRUM E UIPPED WITH MIXING BLADES LOCATED ON A CENTRALDRIVE SHAFT Filed Oct. 30, 1967 2 Sheets-Sheet 2 A War? UEXJ UnitedStates Patent MIXER WITH MIXER DRUM EQUIPPED WITH MIXING BLADES LOCATEDON A CENTRAL DRIVE SHAFT Paul Stift, 15 Markgrafenstn, 1 Berlin 28,Germany Filed Oct. 30, 1967, Ser. No. 678,947

Int. Cl. B28c /10 US. Cl. 259-178 2 Claims ABSTRACT OF THE DISCLOSUREMixer with a drum containing mixing blades near the bottom and locatedon a central drive shaft, with the blades serving to conduct thematerial along the bottom and sides of the container towards the top andthen return it to the bottom. The shaft having the mixing blades mountedthereon is surrounded by a hollow sheath and the latter is mounted onthe drum.

The invention relates to a mixer with a mixer drum containing mixingblades situated near the bottom of said mixer drum and located on acentral drive shaft.

Mixers of this type, where the mixing blades conduct the material alongthe bottom and sides of the container towards the top and then return itto the bottom, are already known. With these mixers, the disadvantageexists that the rotating shaft driving the mixing blades propels theparticles of the material to be mixed towards the outside as a result ofthe action of the centrifugal forces arising from this shaft. Theparticles of the material to be mixed are therefore prevented fromreturning to the bottom of the container. As a result of this, theprocess of mixing is impaired and particularly in the vicinity of thedrive shaft, centrifugal dispersion of the particles of the material tobe mixed causes air to enter from above in the direction of the shaft,i.e. the very air which, with a device constructed in accordance withthe invention, is to be beaten out.

The invention aims at producing circumstances where the air forcedoutwards by the mixer at the bottom and the sides does not re-enter atthe central shaft driving the mixing blades. The solution to thisproblem lies in accordance with the invention in an arrangement wherebythe shaft bearing the mixing blades is surrounded by a hollow sheatharranged on the mixer drum in a manner known as such. As a result of thearrangement of the hollow sheath on the mixer drum, the said sheathremains fixed and the rotating shaft of the mixer is screened by saidhollow sheath so that the rotary motion of the shaft cannot impair theprocess of mixing. Moreover, the hollow sheath surrounding the shaftalso prevents air from entering the mixer from the top in the directionof the shaft. Thus pursuant to this solution and in accordance with theinvention, the air contained in the material to be mixed is beaten outto an extent not previously achieved.

Devices for mixing liquids incorporating a shaft bearing mixing blades,said shaft being surrounded by a casing, are already known. This casingis provided to permit lubrication of the central shaft. The casing in acertain sense forms a lubrication bearing for lubricating the shaftdriving the mixing blades. It is thus provided with an oil inlet and anoil level probe so that the oil level within 3,516,646 Patented June 23,1970 the casing can be measured by means of the oil level probe in amanner similar to that encountered with motor vehicle engines. Thisknown design is therefore quite different from the object of theinvention.

The invention also provides for the possibility of incorporating abeating cross in the vicinity of the bottom of the drum at the lower endof the shaft projecting from the hollow sheath and also a transportblade situated above said beating cross at a distance from this cross.The beating cross and the transport blade are best fixed to areplaceable shaft adapter preferably designed in the shape of atruncated cone. A sealing device and a ball bearing system can also beincorporated at the lower end of the hollow sheath. A plain featherconnection for interchangeable attachment of the motor which is situatedabove the drum can be incorporated at the upper end of the shaft. Thehollow sheath can also be interchangeably suspended in the drum by meansof a flange at its upper end.

FIG. 1 is a section view of the device; FIG. 2 is a bottom view of theadapter and FIG. 3 is a side view of the adapter.

At the upper end of the mixer drum 1 a ring 2 is Welded in- The flange 3of the hollow sheath 4 lies on the ring 2. The hollow sheath 4 which mayhave an external shape matching the prevailing proportions surrounds theshaft 5 at a distance. The drive motor 5 which is provided with a flange7 is situated above the shaft 6.

The three flanges 2, 3 and 7 are connected together by means of thebolts 8 in such a manner that the flanges 3 and 7 with the related parts4 and 6 can be removed by simple operation of the screws 8 which can bescrewed into the flange 2 fixed firmly to the drum 1.

The shaft 5 is detachably connected to the motor shaft end by means ofthe plain feather connection 9. Rotation of the shaft end 10 istransmitted to the shaft 5 via the plain feather connection 9.

A sealing device 11 and a ball bearing system 12 are incorporated at thelower end of the hollow sheath 4. The interior of the hollow sheath 4 issealed off by the sealing part 11. The shaft 5 is rotatably suspended inthe hollow sheath 4 by the ball bearing system 12.

A shaft adapter piece 13 is interchangeably incorporated at the lowerend of the shaft 5 by means of a bolt 14 and a suitably tapered end ofthe shaft 5 fitting into a related socket in the adapter piece 13 asrepresented at 15. At the lower end of the shaft adapter piece 13 in thevicinity of the bottom 16 of the drum is incorporated a beating cross 17and at a distance above this a transport blade 18.

The material to be mixed is introduced into the drum 1 through anopening which is not represented and is drained oif on completion of theprocess of mixing at the bottom of the drum.

With a mixer constructed in accordance with the invention it is possibleto use normal gravel which may be taken directly from the building site,i.e. gravel which has not been screened into individual fractions, whilestill producing a concrete which meets the requirements as regardsquality. Concrete mixed in accordance with the invention does not, aswas hitherto necessary, need to be submitted to vibration treatment atthe location of the application in order to provide further compression.Only a small amount of certain fractions of gravel must be added for themanufacture of concrete even if the gravel as mentioned above has notbeen previously screened. In addition to the advantages of designs orimprovements pursuant to the invention, the wear and tear of parts whichwere previously exposed to exacting demands is less and such parts canbe readily changed.

What is claimed is:

1. A mixer comprising a central drive shaft, a mixer drum containingmixing blades situated near the bottom thereof and located on thecentral drive shaft, the blades serving to conduct a material along thebottom and sides of the drum towards the top and then return it to thebottom of the drum, a hollow sheath surrounding the shaft which has themixing blades mounted thereon and arranged on the mixer drum, means tosupport the blades and shaft in the mixing drum, an interchangeableshaft adapter mounted on an end of the central drive shaft and being inthe form of a truncated cone, means passing centrally of the adapter forsecuring the adapter to the central drive shaft, and a beating crosssecured on the truncated cone on an end thereof.

4 2. A mixer according to claim 1, in which a transport blade member isprovided mounted on the truncated cone and spaced from the beatingcross.

References Cited UNITED STATES PATENTS ROBERT I. JENKINS, PrimaryExaminer U.S. Cl. X.R.

